Exploring the microvascular impact of red blood cell transfusion in intensive care unit patients

Microcirculatory Alterations in Cardiac Surgery: A Comprehensive Guide

Microcirculation is essential for cellular life and its functions. It comprises a complex network of capillaries, arterioles, and venules, which distributes oxygenated blood across and within organs based on regional metabolic demands. Because previous research indicated that organ function is linked to microcirculatory function, it is crucial to maintain sufficient and effective microcirculatory function during major surgery. Impaired microcirculation can lead to inadequate tissue perfusion, potentially resulting in perioperative complications and an unfavorable outcome. Indeed, changes in microcirculation in cardiovascular disease and cardiac surgery have a direct correlation with prolonged stays in the postoperative intensive care unit and high mortality rates within 30 days. Additionally, cardiopulmonary bypass, a regularly employed method in cardiac surgery, has been proven to induce microcirculatory malfunction and, thus, lead to postoperative multiple organ dysfunction. As global hemodynamic parameters can remain stable or improve, whereas microcirculation is still compromised, tracking microcirculatory variables could lead to the development of targeted microcirculatory treatment within hemodynamic management. Therefore, it is necessary to enhance the use of microcirculatory monitoring in the medical domain to assist physicians in the therapeutic management of patients undergoing cardiac surgery. This potentially can lead to better hemodynamic management and outcomes. This review article concentrates on the use of handheld video microscopes for real-time microcirculatory assessment of cardiac surgery patients in the immediate and early postoperative period. Emphasis is placed on integrating microcirculatory monitoring with conventional hemodynamic monitoring in the therapeutic management of patients undergoing cardiac surgery.

Low grade intravascular hemolysis associates with peripheral nerve injury in type 2 diabetes

Type 2 diabetes (T2D) induces hyperglycemia, alters hemoglobin (Hb), red blood cell (RBC) deformability and impairs hemorheology. The question remains whether RBC breakdown and intravascular hemolysis (IVH) occur in T2D patients. We characterized RBC-degradation products and vesiculation in a case-control study of 109 T2D patients and 65 control subjects. We quantified heme-related absorbance by spectrophotometry and circulating extracellular vesicles (EV) by flow cytometry and electron microscopy. Heme-related absorbance was increased in T2D vs. control plasma (+57%) and further elevated in obese T2D plasma (+27%). However, large CD235a+ EV were not increased in T2D plasma. EV from T2D plasma, or shed by isolated T2D RBC, were notably smaller in diameter (-27%) and carried heme-related absorbance. In T2D plasma, higher heme-related absorbance (+30%) was associated to peripheral sensory neuropathy, and no other vascular complication. In vitro, T2D RBC-derived EV triggered endothelial stress and thrombin activation in a phosphatidylserine- and heme-dependent fashion. We concluded that T2D was associated with low-grade IVH. Plasma absorbance may constitute a novel biomarker of peripheral neuropathy in T2D, while flow cytometry focusing on large EV may be maladapted to characterize RBC EV in T2D. Moreover, therapeutics limiting IVH or neutralizing RBC breakdown products might bolster vasculoprotection in T2D.

Association between in-ICU red blood cells transfusion and 1-year mortality in ICU survivors

BACKGROUND

Impact of in-ICU transfusion on long-term outcomes remains unknown. The purpose of this study was to assess in critical-care survivors the association between in-ICU red blood cells transfusion and 1-year mortality.

METHODS

FROG-ICU, a multicenter European study enrolling all-comers critical care patients was analyzed (n = 1551). Association between red blood cells transfusion administered in intensive care unit and 1-year mortality in critical care survivors was analyzed using an augmented inverse probability of treatment weighting-augmented inverse probability of censoring weighting method to control confounders.

RESULTS

Among the 1551 ICU-survivors, 42% received at least one unit of red blood cells while in intensive care unit. Patients in the transfusion group had greater severity scores than those in the no-transfusion group. According to unweighted analysis, 1-year post-critical care mortality was greater in the transfusion group compared to the no-transfusion group (hazard ratio (HR) 1.78, 95% CI 1.45-2.16). Weighted analyses including 40 confounders, showed that transfusion remained associated with a higher risk of long-term mortality (HR 1.21, 95% CI 1.06-1.46).

CONCLUSIONS

Our results suggest a high incidence of in-ICU RBC transfusion and that in-ICU transfusion is associated with a higher 1-year mortality among in-ICU survivors. Trial registration ( NCT01367093 ; Registered 6 June 2011).

Exaggerated Microvascular Vasodilating Responses in Cirrhotic Patients With Septic Shock

OBJECTIVES

Cirrhosis is associated with hemodynamic and vascular disorders. However, microvascular reactivity of cirrhotic patients in the context of sepsis has poorly been investigated.

DESIGN

Prospective observational study.

SETTING

Medical ICU in a tertiary teaching hospital.

PATIENTS

We prospectively included adult patients admitted in the ICU for septic shock with and without cirrhosis. After initial resuscitation, global hemodynamic parameters were recorded and skin microvascular reactivity to local acetylcholine iontophoresis was measured.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thirty patients with septic shock were included (60% male), 10 with cirrhosis and 20 without, with a median age of 61 years (54-74 yr). Cirrhotic patients were mainly classed as Child-Pugh C (80%) and all of them had ascites. Sequential Organ Failure Assessment score and ICU mortality of cirrhotic patients were higher than the noncirrhotic patients, respectively (6.5 [5.0-8.3] vs 11.5 [9.0-14.0]; p < 0.01; 15% vs 70%; p < 0.01). Peripheral tissue perfusion and global hemodynamic parameters were not different between the cirrhotic and noncirrhotic patients but arterial lactate level was three times higher in patients with cirrhosis (6.0 mmol/L [3.9-8.0 mmol/L] vs 2.0 mmol/L [0.9-3.5 mmol/L]; p < 0.01). Basal skin microvascular blood flow was not statistically different between the groups (4.94 perfusion units [3.45-8.73 perfusion units] vs 6.95 perfusion units [5.24-8.38 perfusion units]; p = 0.29). After acetylcholine simulation, skin microvascular blood flow increased more in cirrhotic patients than in noncirrhotic patients (644% [217-966%] vs 169% [73-505%], p = 0.03). Global microvascular reactivity was seven times higher in cirrhotic patients (area under the curve, 16,412 perfusion units [13,898-19,041 perfusion units] vs 2,664 perfusion units [969-4,604 perfusion units]; p < 0.001).

CONCLUSIONS

We identified an exaggerated vasodilating microvascular response in cirrhotic patients with septic shock. Such a result may explain vasopressor resistance and paves the way for future therapeutic trials, targeting nitric oxide pathway specifically in this population.

Extracellular Vesicles in Autologous Cell Salvaged Blood in Orthopedic Surgery

(1) Background: Cell salvage is highly recommended in orthopedic surgery to avoid allogeneic transfusions. Preparational steps during cell salvage may induce extracellular vesicle (EV) formation with potential thrombogenic activity. The purpose of our study was to assess the appearance of EVs at retransfusion. (2) Methods: After ethics committee approval and informed consent, blood was withdrawn from the autotransfusion system (Xtra, Sorin, Germany) of 23 patients undergoing joint arthroplasty. EVs were assessed by flow cytometry in two times centrifugated samples. EVs were stained with specific antibodies against cellular origins from platelets (CD41), myeloid cells (CD15), monocytes (CD14), and erythrocytes (CD235a). The measured events/µL in the flow cytometer were corrected to the number of EVs in the retransfusate. (3) Results: We measured low event rates of EVs from platelets and myeloid origin (<1 event/µL) and from monocytic origin (<2 events/µL). Mean event rates of 17,042 events/µL (range 12–81,164 events/µL) were found for EVs from red blood cells. (4) Conclusion: Retransfusate contains negligible amounts of potentially thrombogenic EVs from platelet and monocytic origin. Frequent EVs from erythrocytes may indicate red blood cell destruction and/or activation during autologous cell salvage. Further research is needed to investigate the clinical relevance of EVs from salvaged red blood cells.

Factors associated with delirium after cardiac surgery: A prospective cohort study

Background:

Delirium is a frequent complication after cardiac surgery and is associated with a higher incidence of morbidity and mortality and a prolonged hospital stay. However, knowledge of the variables involved in its occurrence is still limited; therefore, in this study, we evaluated the perioperative risk factors independently associated with this complication.

Methods:

This study was conducted in a referral tertiary care university hospital with a cardiovascular focus. A total of 311 consecutive adult patients undergoing any type of cardiac surgery were evaluated. The subjects were examined at regular intervals in the postoperative period using the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) tool.

Results:

The incidence of postoperative delirium (PD) was 10%. Among the 18 pre-, intra- and postoperative variables evaluated, the logistic regression analysis showed that low education level, history of diabetes or stroke, type of surgery, prolonged extracorporeal circulation, or red blood cell transfusion in the intra- or postoperative period were independently associated with delirium after cardiac surgery. An increased body mass index was identified as a protective factor.

Conclusions:

The aforementioned risk factors are significantly and independently associated with the presentation of PD. Because some of these factors can be treated or avoided, the results of this study are highly relevant to reduce the risk of this complication and improve the care of patients undergoing cardiac surgery.